When i click on SharePoint "My Profile" it shows 404
It takes me to www.myserver/my/Person.aspx?accountname=abc
We use FBA authentication. How to fix it?
Seems like you didn't followed proper steps to set up User Profile Service application in your farm.
The possible problem could be that there isn't a site collection set up using the appropriate template in the MySite web application.
Check this Article on MSDN providing solution to your problem,
To resolve this issue, move the personal site provider for My Site personal sites to a different site location. To do this, follow these steps: Add an explicit inclusion included path for My Sites personal sites. To do this, follow these steps:
Start SharePoint 3.0 Central Administration.
Click Application Management.
On the Application Management page, click Define managed paths under SharePoint Web Application Management.
In the Web Application box, click the Web application that you want to configure.
In the Add a New Path area, type the path in the Path box. Then, click Check URL to verify the URL.
In the Type box, click Explicit inclusion, and then click OK.
Create a new site collection at the URL that you specified in the included path. To do this, follow these steps:
On the Application Management page, click Create site collection under SharePoint Site Management.
In the Web Application box, click the Web application that you want to configure. On the Create Site Collection page, specify a title and a description for the site collection in the Title and Description area.
In the Web Site Address area, specify the URL of the included path that you added in step 1.
In the Primary Site Collection Administrator area and in the Secondary Site Collection Administrator area, specify the administrator for the site collection.
In the Quote Template area, specify the template that you want to use.
In the Template Selection area, click My Site Host in the Select a template box, and then click OK.
Move the personal site provider. To do this, follow these steps:
Under Shared Services Administration, click Shared Service Provider (SSP).
On the home page, click My Site settings under User Profiles and My Sites.
On the My Site settings page, type the URL of the included path in the Personal site provider box in the Personal Site Services area.
Configure the options that you want for the other settings, and then click OK.
Hope it helps.
The issue can be caused by a few things. 404 however points to a non existing page.
To trace the issue:
I'll think of more things to check and edit my answer later.